Drafting instrument



' Dec. 1, 1942.

J. L. BiXBY DRAFTING INSTRUMENT Filed April 29, 1941 Patented Dec. 1, 1942 DRAFTING INSTRUMENT John Lewis Bixby, Arlington, Mass., assignor to Robert G. Dexter, Boston, Mass.

, Application April 29, 1941', Serial No. 390,917

' 3 Claims. (01. 32,4107) My, invention relates to drafting instruments and comprises an instrument with which a draftsman can automatically draw a series of parallel broken lines or single broken lines as desired.

Various devices have been used in connection with pens in order to make it possible to draw broken lines automatically, but I know of no such device or instrument capable of use with a pencil. In the face of the present urge to save time in making drawings and blueprints, draftsmen are omitting the step of inking in drawings before the blueprints are made. Therefore it is important to promote the more accurate use of the pencil.

Briefly speaking, my invention comprises a transparent block having a longitudinal slot, and a strip of flexible material secured to the block and provided with a series of spaced slots disposed beneath the slot in the block. The slot in the block guides the pencil and keeps it moving in a straight line while the slots in the strip provide the pattern for the broken line.

The advantages and details of my invention will be best understood and appreciated from the following description of a preferred embodiment thereof, selected for purposes of illustration and shown in the accompanying drawing, in which,

Fig. 1 is a plan view of a drafting instrument constructed according to my invention,

2-2 of Fig. 1, 7

M of the block ID. If the instrument is placed with the strip 20 against a sheet of paper, a pencil can be drawn along the slot l4 of the block to, the pencilreaching the paper only in the areas of the slots 22. Thus a broken line will be produced on the paper in one stroke of, the pencil.

Fig. 3 is a view in cross-section along the line 3-3 of Fig. 1.

material such as cellulose acetate or other transparent plastic. The block l0 should be thick enough to be fairly stifi and rigid but still capable of being bowed somewhat. Cut into the block In is a longitudinal slot l 4 having straight sides and bounded at the upper surface of the block by a dished portion l2. v

In both ends of the block H) the edges are transversely slit as shown at IS, the slits'entering farther into the block at one side than the other. The lower edges of'the ends of the-block Ill are undercut.

A thin strip 20 of transparent material is provided with a centrally located row of short, spaced slots 22. The ends of the strip 20 are bent over and flt into the slits H5 in the edges of the block Ill. The block is bowed downwardly, allowing the strip 20 to be snapped in place. The tapering of the slits I6 serves to wedge the strip 20 tightly in place.

22. or the strip 20 lies directly beneath the slot It will be seen that the series of spaced slots If the pencil is canted so that it meets one of the upper edges of the slot [4 and so that its point reaches the paper at the opposite lower edge of the slot M, the instrument will make it possible to draw a series of parallel broken lines. After one line has been drawn, the pencil is moved to vertical position and the instrument is moved until the point of the pencil is struck by the advancing edge of the slot I4. The other edge of the slot M has then moved a distance almost equal to the width of the slot [4. Then 1 the pencil is used to draw another broken line, resting against the same edge of the slot H as before.

The advantages of the instrument of my invention will be apparent, to those skilled in the art,

from the foregoing vdescription of a preferred embodiment thereof.

It will be understood that different effects can be obtained by. changing the dimensions of the slots in the block and the strip. Also the strip may be fastened to the block by means other than that specifically described herein. 7

Having thusdescribed my inventionwhat I claim as new and desire to secure by Letters Patent of the United States is:

1. A drafting instrument which comprises an elongated transparent block provided with a narrow longitudinal slot, the end edges of the transparent block being provided with slits, a flexible strip of transparent material having folded ends adapted to be fitted into the end slits in said block and having. a series of spaced slots extending longitudinally therein and disposed beneath the slot in said block.

2. A drafting instrument which comprises a transparent block having a longitudinal slot and slits in the edges of the ends thereof, a thin strip of flexible material having its ends bent over to fit into the end slits of the block and a series the end edges of the block, whereby the strip may be detachably secured to the block so that the slots in the strip underlie the long slot in the block.

JOHN LEWIS BIXBY. 

